Sealing device and method of producing the same

ABSTRACT

A sealing device for sealing a first side against a second side of a machine part, wherein the sealing device has a sealing element which contacts a counter element. At least a part of the sealing element and/or at least a part of the counter element is coated with a layer consisting of or containing fullerene-like carbon nitride (FL-CNx), wherein an inter-layer of chromium (Cr) or aluminum (Al) or molybdenum (Mo) or titanium (Ti) or tungsten (W) or a diamond-like coating (DLC) or a metal-mix diamond-like coating (Me-DLC) is arranged between the surface of the sealing element and the layer consisting of or containing fullerene-like carbon nitride and/or between the surface of the counter element and the layer consisting of or containing fullerene-like carbon nitride.

TECHNICAL FIELD

The invention relates to a sealing device for sealing a first sideagainst a second side of a machine part, wherein the sealing device hasa sealing element which contacts a counter element. Furthermore, theinvention relates to a method of producing such a sealing device. Theinvention is suitably applied to a plurality of different sealingdevices, especially in the field of bearing technology.

BACKGROUND

For many applications sealing devices are required which seal a firstside of a machine part against a second side of it. E. g. an oil side(first side) has to be sealed against an air side (second side) at ashaft of a combustion engine. Also, in many cases a bearing arrangementhas to be sealed which is done by sealing devices of the kind mentionedabove. Such sealing devices and their sealing elements are under highload as often they have to be pressed against their counter element bybiasing means, e.g. springs, to ensure tightness of the sealingarrangement. Therefore, attempts have been made to strengthen thedurability of the sealing elements. This applies especially iflubrication conditions are poor.

For metal parts different methods for applying coatings are known. Mostof them are not applicable for sealing elements which consists normallyof rubber material, elastomer material and especiallypolytetraflourethylene (PTFE).

For example U.S. Pat. No. 6,340,245 B1 describes a roller bearing havingan inner ring, an outer ring and rolling elements which are in rollingcontact with the raceways of the rings. The rolling elements as well asthe raceways of the rings are coated with a metal-mixed diamond-likecarbon layer. Especially, the respective elements are coated with ametal-mixed diamond-like carbon coating comprising alternating layers ofpredominantly diamond-like carbon, but containing some metal carbide,and layers of predominantly metal carbide, but containing some of thediamond-like carbon.

SUMMARY OF THE INVENTION

While the resistance against high stresses is improved by the describedcoating of the parts it is disadvantageous that the elasticity of thepre-known coatings is quite low. This can lead to cracks during the useof the sealing device so that the adhesion of the coating isjeopardized. As a result, the effective lifetime of the sealing deviceis reduced if damages of the coating take place. Of course, this isespecially disadvantageously if sealing elements of bearings areconcerned.

Therefore, it is an object of the invention to propose an improvedsealing device, which has better properties especially with respect tothe durability of the sealing element.

The solution of this object according the invention is characterized inthat at least a part of the sealing element and/or at least a part ofthe counter element is coated with a layer consisting of or containingfullerene-like carbon nitride (FL-CNx), wherein an inter-layer ofchromium or aluminium or molybdenum or titanium or tungsten or adiamond-like coating or a metal-mix diamond-like coating is arrangedbetween the surface of the sealing element and the layer consisting ofor containing fullerene-like carbon nitride and/or between the surfaceof the counter element and the layer consisting of or containingfullerene-like carbon nitride. Thus, at least a part of the surface ofthe sealing element and/or the counter element is coated with a layerconsisting of or containing a functional part of fullerene-like carbonnitride.

Preferably, the contact area between the sealing element and the counterelement is coated with the layer.

The sealing element can consist of rubber material, of elastomermaterial or of polytetraflourethylene (PTFE). It can be pressed againstthe counter element by means of a spring.

The bonding of the layer to the sealing element and/or the counterelement is significantly improved with use of the inter-layer ofchromium, of aluminium, of molybdenum, of titanium or of tungsten whichis arranged between the surfaces of the sealing element and the layerconsisting of or containing fullerene-like carbon nitride and/or betweenthe surfaces of the counter element and the layer consisting of orcontaining fullerene-like carbon nitride.

Also it is possible and beneficial that an inter-layer of a diamond-likecoating (DLC) or of a metal-mix diamond-like coating (Me-DLC) isarranged between the surfaces of the sealing element and/or the counterelement and the layer consisting of fullerene-like carbon nitride. Theapplication of such diamond-like coatings or metal-mix diamond-likecoatings is quite easy (see e.g. the above mentioned U.S. Pat. No.6,340,245 B1) and a coating of fullerene-like carbon (FL-CNx) can beadded. Additional benefits can be obtained where a top surfacefunctionalization is desired, e.g. for designed surface energy to suit agiven lubricant/oil.

The thickness of the layer consisting of fullerene-like carbon nitrideis preferably between 0.1 μm and 10 μm, especially between 0.1 μm and 1μm. The thickness of the inter-layer is preferably between 1 nm and 5μm, preferably between 25 nm and 5 μm. Plasma processed or arc-etchedsurfaces (no actual deposition, but implantation) with components likeCr and Ti as well as diffusion bonded components work as well.

The layer consisting of fullerene-like carbon nitride is deposited onthe sealing element and/or the counter element preferably by means ofmagnetron sputtering. Also it is possible that the layer consisting offullerene-like carbon nitride is deposited on the sealing element and/oron the counter element by means of physical vapour deposition (PVD), bymeans of chemical vapour deposition (CVD) or by means of a hybridsthereof, any of which or combined process can include some plasma forlimited ion assistance to the coating during or after deposition. I. e.fullerene-like carbon nitride coatings implemented in a graded ormultilayered coating with any type of diamond-like carbon is alsobeneficial and would give improvement compared with DLC alone.

In one embodiments of the invention, deposition process temperatures forthe sealing element and/or the counter element are kept below 180° C.,preferably at or below 150° C.

With regard to the fullerene-like carbon nitride according to theinvention the following remarks are made:

Carbon nitride thin film materials has been described in “Fullerene-likeCarbon Nitride; A Resilient Coating Material” from Lars Hultman, JörgNeidhardt, Niklas Hellgren, Hans Sjöström, and Jan-Eric Sundgren inMaterials Research Society Bulletin, 28 (March), 2003, 194. In thisreference the nature of fullerene-like carbon nitride (FL-CNx) ispresented. This patent application involves an original application andthe invented solution to process fullerene-like carbon nitride coatingsfor sealing elements in different applications including adhesiontechnology and the optimum layer thickness of each required layer. Also,the process temperature allowing for different sealing materials isgiven.

Preferably, unlike the pure carbon fullerene molecules which do not formstrong materials, the present invention uses fullerene-carbon nitridecoatings for sealing devices which represent an originalfunctionalization of the fullerenes as dense, solid, well-adheringcoatings that can be fabricated for benefits stated in this application.The functionalization is obtained by the doping or alloying by nitrogento the carbon during a coating deposition processes described herein.

The carbon structure family was completed by a new modification of purecarbon. In 1990 the discovery of the fullerenes was done and thepossibility for the production of fullerenes in large amounts wasachieved (see W. Krätschmer, L. D. Lamb, D. R. Huffman, Nature 347(1990) 354). Fullerenes are polyeders build up by n three timecoordinated carbon atoms with 12 pentagons and n hexagons, were theminimum for n is equal 20. Fullerenes fulfill the EULER's theorem, wherea polyeder build up from pentagons and hexagons has to contain exactly12 pentagons, to build a closed structure. Following this rule, thedodekaeder with 20 carbonatoms is the smallest possible fullerene.Actual the smallest fullerene is the C₆₀, because important for thestability of the structure is, that no pentagons are side by side. Thisis described by the Isolated Pentagon Rule (IPR). If two pentagons arejoined, the tension of the binding is increasing and the structure isnot anymore energetically stable.

The carbon atoms in fullerenes each have three neighbours and all bondsmore or less saturated. Thus, in chemical reactions fullerenes are notreacting aromatic (“superbenzene”), they show aliphatic behavior withweak bonding of fullerene molecules. Good solvents for fullerenes areCS₂, o-dichlorobenzene, toluene and xylene. Fullerenes are insoluble inwater and stable in air. Thin layers of fullerenes are coloured fromyellow to yellow-green. For the effects of doping with nitrogen, theonly nitrogen-containing fullerenes formed in nature by wet-chemicalmethods is the C₅₉N₁ so called aza-fullerene. It readily dimerizes toform {C₅₉N₁}₂ molecules and thus becomes inert. The present inventionhere is to preferably use a vapour deposition method which can be usedto grow solid coatings of carbon nitride that consists ofnitrogen-containing (aza-)fullerene fragments. In the cross-linked formthey give the strength needed for a bearing application. The presentedprocess is a practical and technologically viable process tofunctionalize otherwise relatively inert fullerenes by depositing thematerial with a synthetic growth.

The fullerene-like (FL) structure derived for sealing devices arisesfrom the presence of bent and cross-linked graphitic basal planes (alsoknown as graphene). This specific functionalization of the fullerenes isobtained by the precise insertion of nitrogen atoms substituting forcarbon in the graphene planes such that the carbon coordination isretained, but that the extra electron provided by each nitrogen atompromotes the formation of pentagon rings that is geometrically requiredto obtain the plane bending (its fullerene-likeness), but also offercross-linking sites. This structure results in a compliant and toughmaterial at the same time (high elastic recovery, >80%) that is herepresented for use as an original coating material to sealing devices.

It is a central part of the present invention that the fullerene-likecarbon nitride material structure for coatings is a much differentmaterial to pure carbon fullerenes and fullerides (crystallized forms offullerene molecules with or without doping of metals). The lattermaterial is relatively soft and has much less elasticity and noresiliency compared to the FL-CNx compounds.

Fullerene-like carbon nitride is also qualitatively different todiamond-like carbon as the latter have (predominantly) four-foldcoordinated carbon atoms and the former exclusively three-foldcoordination. In a useful quality, the fullerene-like carbon nitridecoating has a similar low-friction performance as non-hydrogenated DLC.

In a further definition of the fullerene-like CNx according to thisinvention, it is qualitatively being non-crystalline and different fromany crystalline form of carbon nitride, such as in pre-known beta-C3N4,alfa-C3N4 or other compound or phase. It is significant that thefullerene-like CNx according to the invention is not crystalline thus itdoes not (by definition) form part of any superlattice based carbon- andnitrogen-containing material.

Preferably, the production of fullerene-like CNx is done by magnetronsputtering, but practically all physical vapour (PVD) and chemicalvapour deposition (CVD) processes including some plasma for limited ionproduction and hybrids thereof can be used to produce the coating.Important parameters for the growth of the substance are the substratetemperature (below 180° C. up to 500° C.) is also crucial withtemperature sensitive precision bearing components, where hightemperatures will result in none uniform dimensional changes and loss ofprecision and can reduce the load carrying capacity of the substrate dueto softening. Unbalanced reactive magnetron sputtering of a graphitetarget in a nitrogen-containing atmosphere as a preferred technique isessential for the growth of fullerene-like CN_(x) structures due toC_(x)N_(y) molecules (especially CN and/or C₂N₂ or complexes thereofmolecules), which are formed in the process or can be added to theprocess as they act as precursors or growth templates for the intendedstructure for best coating performance. This understanding makes itpossible to intentionally add such molecules by a gas source forpossible promotion of the fullerene-like structure.

The deposition process is best described as a hybrid of plasma vapourdeposition and chemical vapour deposition. In the discussedfullerence-like structure, deformation energy is predominantly storedelastically and released after load removal giving it a tough andresilient character. In addition, the relatively low modulus leads to aspreading of the contact stresses over a larger volume and consequentlyto low stress gradients at the substrate/film interface. This hinderssubstrate/film delamination under load and therefore results in a highload bearing capability, while the coating asperities behave elasticallywith no tendency to brittle fracture in tribological contact.

The sealing device according to the invention shows differentadvantages:

Due to the low deposition temperature the coating can be applied to anysealing element without being detrimental to the fatigue property of thecontact and without material micro-structural changes which would leadto unfavorable dimensional variation of the element.

The adhesion of the coating to the substrate (sealing element or counterelement) can be at a level sufficient for carrying friction contactfatigue stresses in the GPa range (3-4 GPa) with the appropriate choiceof inter-layer and inter-layer structure.

Cohesion within the coating is also high and is enhanced by the crosslinking and curvature of the fullerene-like nano-to-micro-layers andconvoluted microstructure.

The super-elastic characteristic of the coating allows it to absorblocally large deformations from handling damage or particle denting, ina purely elastic way. The initiation of micro-cracks—due to plasticweakening—is avoided. High stress concentrations associated tomicro-crack tips are also avoided. In this way crack initiation andpropagation (characterizing rolling contact fatigue and surfaceinitiated failure) is either avoided or at lease drastically reduced.

Under marginal or no lubrication the fullerene-like coating provides alow coefficient of friction compared to that one of rubber-steel contactand at least as good as for non-hydrogenated DLC-steel. In this way,adhesive wear damage and scuffing initiation/propagation is avoided orat least drastically reduced.

Further, the coating has very good wetting behaviour which enhancestransport and retention of lubricant fluid into the (rolling or sliding)contact. Therefore the coating will improve the lubrication condition ofthe contact in case of lubricant starvation or marginal lubricationconditions. The coating can be used for this purpose when applied as anadditional processing step to any contemporary DLC-coated bearingtechnology as mentioned above.

By virtue of the concurrent coating surface etching of the presenteddeposition process, less strongly bonded growth species at surfaceprotrusions are preferentially removed. Thus, the coating can also beapplied to obtain a levelling of the substrate surfacemicro-geometry/micro-topography. This is leads to very smooth contacts(suitable for thin film lubrication) and reduce run-in effects for thebearing.

The coating will also ensure a long service life for sealing devicesworking with high contamination level in the lubricant. In such casesthe coating will reduce the abrasive wear damage due to the combinedaction of hardness low-friction coefficient, high fracture toughness andsuper-elasticity. This is also the case with none abrasive particlessuch as ‘soft’ metallic contaminants where indentation are formed withraised edges, where subsequent over rolling will give enhanced stresslevels at theses raised edges and can result in early surface initiatedfailures. The presence of such a coating, which also acts in a superelastic manner, will alleviate such effects leading to delayed failureor prevention of failure under contaminated conditions

I. e. the mechanical properties of the sealing device are improved,especially the sealing element has a longer life time and betterabilities to keep its shape with respect to possible wear to make suretightness of the device. Contamination of the sealing device does nothave a big influence.

Fullerene-like carbon nitride (FL-CNx) compound as a resilient coatinghas elastic recovery values of ≧70% as determined by nanoindentationmeasurements. Said FL-CNx coating consists predominantly of carbon inthe form of bent and cross-linked graphene planes in which N atomssubstitute for C to induce the formation of odd-membered rings,preferably pentagons, so as to induce the fullerene-likeness. Thecorresponding structure can be determined by electron microscopymethods. N is a structurally integrated in the FL-CNx coatings and assuch it yields the cross-linking of fullerene-like structural units. Thecorresponding bonding can be determined by spectroscopic methods. Therange of nitrogen contents in the FL-CNx coatings covered by theinvention is preferably between 1 and 35 at.-%. Doping or alloying byelements other than N, in particular P, S, and B, by itself or incombination with N that gives FL-CNx coatings are also beneficial withregard to the solution of the above mentioned object.

In some pre-known application the use of hexagonal boron carbon nitrideis proposed. Hexagonal boron carbon nitride is different fromfullerene-like carbon nitride according to the present invention in twoways:

A first aspect is that there is B (boron) in one and not in the other.

A second important aspect is that the hexagonal phase has an orderedlattice bonding different from FL-CNx. In fact FL-CNx has C bonded inpentagons which is not the case for the other. Both chemistry andbonding structure determine a material. Thus, they are different.

Further preferred embodiments of the invention are defined below and inthe claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawing shows an embodiment of the sealing device according to theinvention.

FIG. 1 shows a sectional view of a sealing device,

FIG. 2 shows the detail “Z” in FIG. 1 in a magnified view and

FIG. 3 shows characteristic properties of two fullerene-like CNxcoatings in comparison to some known technologically importantmaterials.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an example for a sealing device 1. It has a sealing element4, which is carried by a carrier element 11. The sealing element 4consists of elastomer material. It is pressed against a counter element5 by means of a spring 7. The counter element 5 is a sleeve which ismounted on a shaft 12. The carrier element 11 is fixed in a housing part13.

So, an oil side 2 (first side) is sealed against an air side 3 (secondside).

As can be seen in FIG. 1 a further sealing element 14 can be arrangedfor which the same applies as for the sealing element 4 as explainedlater on.

As can be seen in the magnified illustration according to FIG. 2, thesurface 9 of the sealing element 4 and the surface 10 of the counterelement 5 are coated with two layers 8 and 6 each. Layer 8 is a metalliclayer consisting of chromium, of aluminium, of molybdenum, of titaniumor of tungsten. The thickness T of this layer 8 is preferably between 25nm and 5 μm.

On the surface 15 of the layer 8 of the sealing element 4 and on thesurface 16 of the layer 8 of the counter element 5 another layer 6 isarranged. This layer 6 consists of fullerene-like carbon nitride asdiscussed above. The thickness t of the layer 6 is smaller than thethickness T of the layer 8 and is preferably between 0.1 μm and 10 μm.Even a layer thickness below 0.1 μm can be sufficient.

Incorporation of nitrogen in the carbon, which has a hexagonal atomicpattern, helps to develop sturdy bonds with the carbon atoms,transforming the hexagonal graphitic structure into a mixedpentagonal-hexagonal network. This leads to curvature of the networkforming amorphous interlocked multi-layers and fullerene-like shellstructures. The formation of additional tight but flexible bonds (actingas strong hinges) between the fullerene like layers helps to strengthenthe microstructure providing a coating with excellent and noveltribological properties. It is significant that the otherwise relativelyinert carbon fullerene molecules are functionalized by the inclusion ofnitrogen atoms into the structure by the deposition of dense and solidcoatings of fullerene-like carbon nitride.

As mentioned above the coating has a low friction coefficient, with highthermal conductivity, with high hardness and super-elasticity, with hightemperature and chemical stability and with good substrate adhesion andstrength, especially when applied with an inter-layer.

Carbon nitride films (CN_(x)) basically show similar beneficialtribological behavior as diamond like carbon coatings as described inmentioned U.S. Pat. No. 6,340,245 B1. As diamond like carbon, thecoating according to the present invention can be deposited atrelatively low temperatures between 150° C. and approximately 350° C.,typically <240° C. This relatively low deposition temperature will avoiddestruction of the sealing element 4 and/or the counter element 5.

The proposed CN_(x) films exhibit extreme elasticity, which preventsplastic (non-recoverable) deformation and micro-cracking of the coating.This property combined with the low modulus of elasticity has thecapability of dissipating contact loads over large areas/volumesfacilitating the formation of lubricant film. The coatings can thereforebe described as hard (5-30+GPa, typically 8+/−2 GPa) and “rubbery” or“fracture tough” due to its extreme elasticity. The characteristicproperties of two fullerene-like CNx coatings is presented in FIG. 3 incomparison to some known technologically important materials.

With regard to FIG. 3 the following explanations are made:

In this figure the nanoindentiation results are depicted showing themechanical properties as well as the dry sliding friction coefficientversus steel. When a material which experiences both elastic and plasticdeformation is strained by indentation, the behaviour during theloading-unloading cycle is determined by the degree of imposed strainrelative to the yield strain. With E being the Young's modulus (in GPa)and H being the (Meyer) hardness (in GPa) the H/E ratio is a descriptiveparameter for the elastic-plastic behaviour.

As can be seen from FIG. 3 the present invention has preferably a CNxcoating having a H/E ratio above 0.1, preferably above 0.12, especiallybetween 0.12 and 0.2 showing a “super elastic” property.

Basically the coating allows large elastic (recoverable) deformationwithout the initiation of a crack usually associated with the contactfatigue damage process. The super-elastic property of CN_(x) films makesthis material ideal for protective coatings of sealing surfaces. Sealingelements provided with this type of protective coating will drasticallyreduce the chance of surface initiated failure and will have an extendedservice life in all conditions. In particular, dramatic performanceimprovements are expected in case of reduced lubrication (thin film,mixed or dry conditions) and presence of contamination debris in thelubricant.

In the case of localized stress concentration developed at certainlocations of the sealing elements the local film thickness is reduced(due to the contact micro-slip) leading to an increase of the surfacetraction. This causes a further increase of the local temperature andadditional reduction (or collapse) of the lubricant film. The use of theCNx film according to the invention will drastically improve thesurvival capability of the sealing surface affected by dent (or other)damage or in case of reduced film thickness. This is achieved by thecombined action of the super-elasticity and low friction coefficient ofthis film. The super-elasticity will allow the coating to adapt to thedent damage without cracking or faking and the low coefficient offriction will reduce the local traction and adhesive shear stress whichis the primary cause of micro pitting.

During the introduction of contamination particles in the zone betweenthe sealing element and the counter element the low coefficient offriction of CNx will be beneficial to the life of the sealing device.Indeed, the low coefficient of friction of CNx combined with highelasticity will reduce the stress build up during indentation by foreignparticles, leading to shallower and less damaging indentations.

When applying the fullerene-like coating, basically a batch vacuum(single or multi chamber) process is used which is plasma assisted andprovides a vapor of ions, atoms, and molecules of carbon and nitrogenthat are deposited onto the substrate (rings or interlayer). Lowdeposition temperatures are obtained if low energy input to thesubstrate is used. The sealing components to be covered with the layersare pre-cleaned outside the coating vessel. A plasma cleaning processcan follow inside the coating vessel. Afterward, the interlayer 8 aswell as the layer 6 of fullerene-like carbon nitride is applied in thevessel.

Depending on the characterization technique and processing, the coatingsmay also be described as amorphous (such as by XRD analysis) or locallycrystalline (such as by high-resolution electron microscopy) in afullerene-like carbon nitride matrix. In each case, good tribologicalbehaviour has been achieved in for example sliding contacts. Thedeposition temperatures are such that the coatings are not applicable totemperature sensitive materials such as standard sealing material. Thesematerials ideally require that the substrate does not reach temperaturesof above 160° C. Temperatures above this which will result in adestruction.

The amorphous CNx coatings are also limited in terms of adhesion andcohesion and are therefore prone to early coating failure, when contactstresses are high (in the GPa range) and when these are combined withslip or sliding.

A low energy processing window has been established which allows theapplication of CNx to sealing material such that the CNx can be appliedat temperatures of 150° C. The conditions are such that the coatingsalso have a fullerene-like structure which significantly enhances theirload carrying capacity such that application to sealing devices withcontact stresses in the GPa range can be achieved.

The fullerene structural units are also cross linked which dramaticallyincreases their resistance to near surface shear stress, which wouldnormally lead to in plane (cohesive failure of the coating). Thisfeature incidentally is a limit on pre-known Diamond-Like-Coatings(DLCs) and metal-mix DLCs (Me-DLCs).

With respect to the conditions for deposition of fullerene-like CNx itis noted that the ion flux and the beam energy conditions have beenidentified for low temperature deposition of fullerene-like CNx withcross linking.

As explained above, other features of the (magnetron sputtering)deposition process are that metallic inter layers can be added toimprove intrinsic adhesion at or near the interface with the substrateand the layers can be graded into the fullerene-like CNx coating, whichdoes not require pre-cursor inter layers in order to seed the CNxstructure in the upper part of the coating.

REFERENCE NUMERALS

-   1 Sealing device-   2 First side (oil side)-   3 Second side (air side)-   4 Sealing element-   5 Counter element-   6 Layer consisting of or containing fullerene-like carbon nitride-   7 Spring-   8 Inter-layer-   9 Surface of the sealing element-   10 Surface of the counter element-   11 Carrier element-   12 Shaft-   13 Housing part-   14 Sealing element-   15 Surface-   16 Surface-   t Thickness of the layer consisting of or containing fullerene-like    carbon nitride-   T Thickness of the inter-layer

1. Sealing device for sealing a first side against a second side of amachine part, wherein the sealing device has a sealing element whichcontacts a counter element, wherein at least a part of the sealingelement and at least a part of the counter element are coated with alayer consisting of or containing fullerene-like carbon nitride (FL-CNx)and wherein an inter-layer is arranged between a surface of the sealingelement and the layer consisting of or containing fullerene-like carbonnitride and between a surface of the counter element and the layerconsisting of or containing fullerene-like carbon nitride, wherein theinter-layer consists of chromium (Cr) or aluminum (AI) or molybdenum(Mo) or tungsten (W) or a diamond-like coating (DLC) or a metal-mixdiamond-like coating (Me-DLC).
 2. Sealing device according to claim 1,wherein a contact area between the sealing element and the counterelement is coated with the layer consisting of or containingfullerene-like carbon nitride.
 3. Sealing device according to claim 1,wherein the sealing element is comprised of rubber material or ofelastomer material or of polytetraflourethylene (PTFE).
 4. Sealingdevice according to claim 1, wherein the sealing element is pressedagainst the counter element by a spring.
 5. Sealing device according toclaim 1, wherein the layer consisting of or containing fullerene-likecarbon nitride possesses a thickness between 0.1 μm and 10 μm. 6.Sealing device according to claim 5, wherein the thickness of the layerconsisting of or containing fullerene-like carbon nitride is between 0.1μm and 1 μm.
 7. Sealing device according to claim 1, wherein theinterlayer possesses a thickness between 1 nm and 5 μm.
 8. Sealingdevice according to claim 7, wherein the thickness of the inter-layer isbetween 25 nm and 5 μm.
 9. Sealing device according to claim 1, whereinthe layer consisting of or containing fullerene-like carbon nitride isdeposited on the sealing element and on the counter element by magnetronsputtering.
 10. Sealing device according to claim 1, wherein the layerconsisting of or containing fullerene-like carbon nitride is depositedon the sealing element and on the counter element by physical vapourdeposition (PVD).
 11. Sealing device according to claim 1, wherein thelayer consisting of or containing fullerene-like carbon nitride isdeposited on the sealing element and on the counter element by chemicalvapour deposition (CVD).
 12. Sealing element according to claim 10,wherein the layer consisting of or containing fullerene-like carbonnitride is deposited on the sealing elementand on the counter element bya hybrid of physical vapour deposition (PVD) and chemical vapourdeposition (CVD).
 13. Sealing device according to claim 1, wherein thetemperature of the sealing element and the counter element duringdeposition of the layer consisting of or containing fullerene-likecarbon nitride is kept below 180° C.
 14. Sealing device according toclaim 1, wherein elements other than nitrogen (N) are doped, or alloyed,or both, in the fullerene-like carbon nitride.
 15. Sealing elementaccording to claim 14, wherein the elements other than nitrogen (N) thatare doped, or alloyed, or both, in the fullerene-like carbon nitrideinclude one or more of phosphorus (P), sulfur (S), and boron (B). 16.Sealing element according to claim 1, wherein the fullerene-like carbonnitride (FL-CNx) has a ratio H/E>0.1, wherein H is the Meyer hardness(in GPa) and E is the Young's modulus (in GPa).
 17. Sealing elementaccording to claim 16, wherein the ratio H/E>0.12.
 18. Sealing elementaccording to claim 16, wherein the ratio H/E is between 0.12 and 0.2.